The invention relates to heat exchangers and more particularly to shell and tube heat exchangers.
Shell and tube heat exchangers are well known and commonly used in the beverage and dairy industry to transfer heat from the plant steam supply to water or other liquid product. Heat exchangers used in these industries are commonly known as sanitary heat exchangers and must be made from approved materials and are subject to routine inspection. A typical prior art sanitary heat exchanger is shown in FIG. 1. The prior art heat exchanger 10 is designed to rest in the horizontal position supported by a stand or bracket (not shown). A stainless steel shell 14 houses a tube bundle 18 of stainless steel tubes 22. The shell 14 is open on one end to allow insertion and replacement of the tube bundle 18.
The shell 14 includes a flange 26 adjacent the open end of the shell 14. The tube bundle 18 includes a face plate 30 that engages the flange 26 and is secured to the flange 26 when a closure plate 31 is fastened to the flange 26 to seal the open end of the shell 14 and hold the tube bundle 18 in place. The shell 14 also includes a vacuum breaker 32 that allows air to enter the shell 14 and prevent vacuum buildup inside the shell 14.
As is commonly understood, liquid product is pumped into the tube bundle 18 at product inlet 34, circulates through the tubes 22 and exits the tube bundle 18 at product outlet 38. As the product circulates through the tubes 22, relatively low pressure steam enters the shell 14 at steam inlet 42. The steam circulates around the tubes 22 and transfers heat to the fluid product as is commonly understood. As the steam loses its heat, it condenses to water inside the shell 14. The condensate forms on the tubes 22 and falls to the bottom of the shell 14, eventually draining out through the condensate outlet 46. Typically, after installation, the outside of the shell 14 is wrapped with insulating material (not shown) to maximize the efficiency of heat transfer.
While these prior art heat exchangers 10 are designed to operate in the horizontal position shown in FIG. 1, it has been known to stand the heat exchanger 10 in a vertical orientation such that the product inlet 34 and product outlet 38 are at the bottom and the condensate outlet 46 is adjacent the top. The vertical orientation of the prior art heat exchanger 10 serves a number of purposes. First, the vertical orientation occupies less floor space in the plant which enables optimization of floor layout. Second, the vertical orientation allows the product to drain from the tubes 22 under the force of gravity when pumping stops.
Standing the prior art heat exchangers 10 in the vertical position presents a significant problem. When oriented vertically, the condensate outlet 46 is adjacent the top of the shell 14. The condensate that forms in the shell 14 cannot drain through the condensate outlet 46, but rather falls toward the open end of the shell 14 and collects adjacent the flange 26. Typically, the condensate fills the inside of the shell 14 at least to the steam inlet 42 and possibly even higher. This condensate accumulation is disadvantageous for several reasons. First, the condensate corrodes portions of the inside of the shell 14, the outside of the tubes 22, and portions of the flange 26 and face plate 30 that are in direct and constant contact with the accumulated condensate. This can cause the flange 26 and face plate 30 to corrode together, making replacement of the tube bundle 18 more difficult. Furthermore, corrosion can lead to product leakage from the tubes 22, condensate leakage from the shell 14 and the need for premature replacement of the shell 14, tube bundle 18 or both.
Second, the accumulated condensate lowers the efficiency of heat transfer in the heat exchanger 10. Some heat from the steam is transferred to the condensate instead of the product in the tubes 22. Additionally, the heated product passes through the accumulated condensate on its way toward the product outlet 38 and loses some of its newly obtained heat.
To alleviate these problems, the present invention provides a heat exchanger designed to permit substantially complete condensate drainage irrespective of whether the shell is oriented horizontally, vertically or somewhere in between. More specifically, the invention provides a heat exchanger comprising a shell having a closed end, an open end, a steam inlet near the closed end, and a condensate outlet near the open end. Preferably, the shell further includes a flange adjacent the open end, and the condensate outlet is in the flange. Further preferably, the heat exchanger also includes an insulating jacket surrounding the shell, wherein the insulating jacket includes an outer surface and an inner surface engaging the shell, and wherein the insulating jacket includes a metallic shroud on the outer surface.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings.